SQL features
YugabyteDB's YSQL API reuses a fork of the query layer of PostgreSQL as its starting point and runs on top of YugabyteDB's distributed storage layer called DocDB. This architecture allows YSQL to support most PostgreSQL features, such as data types, queries, expressions, operators and functions, stored procedures, triggers, extensions, and so on, all of which are expected to work identically on both database systems.
Tip
A large portion of the documentation and examples written for PostgreSQL would work against YSQL.The following diagram shows how YugabyteDB reuses the PostgreSQL query layer, specifically the components that receive the query (postman), the query parser, rewriter, and analyzer, as well as components responsible for planning and executing the query. Some of these components have been modified to perform efficiently in a distributed SQL database.
SQL features in YSQL
The following table lists the most important YSQL features which you would find familiar if you have worked with PostgreSQL.
| YSQL Feature | Description |
|---|---|
| Schemas and Tables | SQL shell with ysqlsh, users, databases, tables, and schemas |
| Data Types | String, numeric, temporal types, SERIAL pseudo type, ENUM, arrays, composite types |
| DDL Statements | Data definition language |
| Data Manipulation | INSERT, UPDATE, DELETE, INSERT ... ON CONFLICT, and RETURNING clauses |
| Queries and Joins | Queries, joins, FROM, GROUP BY, HAVING clauses, common table expressions, recursive queries |
| Expressions and Operators | Basic operators and boolean, numeric, date expressions |
| Stored Procedures | Support for stored procedures |
| Triggers | Triggers (on data modification) and event triggers (on schema changes) |
| Extensions | Support for PostgreSQL extensions |
Advanced features in YSQL
The following table lists the advanced features in YSQL.
| YSQL Feature | Description |
|---|---|
| Cursors | Declaration of cursors in YSQL |
| Table Partitioning | List, range, and hash partitioning of tables |
| Views | Views and updatable views |
| Savepoints | Savepoints in YSQL |
| Collations | Collations in YSQL |
| Foreign data wrappers | Foreign data wrappers in YSQL |
Going beyond SQL
Because YugabyteDB is a distributed SQL database, YSQL has a number of features that are not present in PostgreSQL, as summarized in the following table.
| YSQL Feature | Description |
|---|---|
| Data distribution with HASH | Enables the use of HASH sort order, in addition to ASC and DESC for indexes |
| Tablespaces | Enables pinning of data in tables and table partitions to different geographic locations |
| Follower Reads | Enables more read IOPS with low latencies in YugabyteDB clusters |